I was travelling in a far galaxy, and I tell myself : "This is a cool place. This star seems to be interresting." Getting closer to it, I noticed its 11 planets, and by clicking randomly on one of them, the type "Warm ice giant" hits me. The temperature of this planet is 300 Kelvin, and water freezes under 273 Kelvin. Isn't strange ? And I remember : "but, if the pressure is high, maybe water could exist at solid form ?"

Jumping on the internet to find the Clapeyron diagram of water :

Noticing that the slope of the MT curve is negative, and the coordinates of the point T are (273.16 K, 611 Pa), I conclude : "Ice can't exist when the temperature is over 274 K". Maybe this planet (RS 6647-2395-9-129926115-4 3) should be called "watered warm giant".

But maybe I just forgot something, and I'm wrong... Expecting your thoughts...

"Ice" in this case does not refer to water ice. In planetary science, the word "ice" refers to a variety of substances, like water, ammonia, carbon dioxide, nitrogen, methane, etc., regardless of their state of matter. Ice giants are predominantly gaseous planets that contain significant quantities of these substances relative to hydrogen and helium. Examples in our system are Uranus and Neptune.

Well, since ice giants are essentially small gas giants with "ices" mixed in, it could be any of them really, just in their gaseous phase. Any of the ones Harbinger mentioned could be part of the ices in the planet.

Also, in 0.95 extremely hot ice giants were actually the most common type of planet because of a bug causing the first planet from solitary stars always to be an ice giant. XD So you saw a lot of these at first sight paradoxical planets.

Water and other "ices" really exist in a solid form under huge pressure. Google for "ice VII" for example. PS: SpaceEngine should have some ingame wiki to prevent such questions in the future. Warm/hot Ice giants and Oceanias, shape of red giants, what else?